STRESS-STRAIN RELATIONSHIPS IN UNIAXIAL EXTENSION OF HIGH CIS-1,4-POLYISOPRENE NETWORKS WITH DIFFERENT MOLECULAR-WEIGHT PRECURSORS

Equilibrium stress-strain relationships in uniaxial extension for high cis-1,4-polyisoprene networks were obtained by extrapolation of relaxation measurements to infinite time through a BKZ constitutive equation. Three series of networks were investigated, each series being characterized by its polymer precursor molecular weight. Influence of crosslinking density was studied through varying amounts of dicumyl peroxide as crosslinking agent. These results were used to test P. J. Flory and B. Erman's recent molecular elasticity theory of imperfect networks with constraints on junctions. It was shown that this later theory treating entanglements as restrictions on junction fluctuations could be used to characterize network topology.